The present invention relates to rescue apparatus which includes as an essential element a rescue hoist designed for lowering or lifting persons or loads quickly and easily without a substantial effort on the part of the operator of the system. Other unique, but optional, components of the system include a centrifugal brake device, a swivel pulley and a handled ascender to be used along with the hoist.
One conventional hoist device includes a rope drum supported on a bolt extending from a bracket by a free wheeling bearing or so-called roller friction clutch which permits the rope drum to freely rotate in one direction (counter clockwise, in the exemplary description) but which blocks rotation of the drum in the opposite direction (clockwise in the exemplary description). In a typical load lowering application, a rope is wound around the drum at least for 11/2 and usually 21/2 (depending on rope diameter) turns so that a braking force is applied to the rope as it glides over the drum surface in the direction in which the drum rotation is blocked. In other words, the braking action results from the friction between the rope and the drum surface as the rope is wound onto and then off the non-rotating drum under the downward loading influence of the person (or object) being lowered. The load end of the rope is generally connected to one or more pulleys downstream of the hoist which provide a mechanical lifting advantage so that the operator need only exert a slight counterpull in order to control the descent of the person being lowered.
Hoisting devices of this type are disclosed in U.S. Pat. Nos. 3,703,218 and 3,807,696. In the latter patent, improved rope guide devices for the rope drum are disclosed. One arc-shaped guide is in the form of two laterally spaced bails arranged along a portion of the circumference of the rope drum and connected at the ends, forming a slot through which the rope may pass. The arrangement is such that one end of the rope, the so-called control end of the rope, may be guided onto the drum through the rope guide slot from various directions relative to the drum.
The '696 patent also discloses a lower rope guide block which comprises a pair of side members and a bridging member interconnecting the side members such that the rope guide block reaches over the space which is taken up on the surface of the rope drum by the turns of the rope. The inwardly facing surfaces of the side members of the guide block and the outwardly facing surface of the rope drum as well as the inwardly facing surface of the bridging member of the guide block, forms a rope guide chamber which has a shape which defines the position of adjacent rope turns where the rope guide block reaches over the outer surface of the rope drum.
Even with the improvements described in the '696 patent, problems remain. For example, it has been determined that there is excessive space between the rope riding on the drum and the arc-shaped rope guide which allows the rope to overlap and tangle. There is also excessive space between the roller drum surface and the arc-shaped rope guide which has caused problems in that, if proper care is not taken, the rope can lift off the roller drum and slip between the roller drum and the arc-shaped rope guide thereby jamming and totally disabling the unit.
In addition, a natural occurrence when raising a load (with the drum rotating in a counterclockwise direction) is for the rope on the drum to "corkscrew" towards the rear of the drum. With no lower rope guide, as new rope comes onto the drum, it will "stack up" and overlap the rope already on the drum. This can occur immediately upon commencing raising and can totally disable the unit. The lower rope guide block of the '696 patent is said to prevent the rope from "stacking up" and overlapping during raising. This is accomplished by positioning the rope guide block such that it prevents the rope on the drum from moving too far back, thus allowing a space for the new rope to come onto the drum. However, this configuration creates a considerable amount of friction between the rope and the lower rope guide block, reducing the system's efficiency and greatly increasing the amount of force required to lift a given load. Moreover, even with the lower rope guide block in place, existing systems have allowed the rope on the drum to overlap and tangle under wet, dirty conditions because as the rope becomes wet and soiled, the friction between the rope and the rope drum increases, allowing the rope to "corkscrew" farther back than normal and thus, wedging under the new rope coming onto the drum.
It is the object of the present invention to provide an improved hoist device which eliminates the problems described above with regard to the drum and the conventional arcuate rope guide and associated lower guide block. Thus, in one aspect of the present invention, the cylindrical rope engaging surface of the drum is modified to include an upwardly and rearwardly directed taper in that portion of the drum closest to the hoist support bracket or backplate. The tapered roller drum prevents overlapping during raising even with no lower rope guide block installed, and thereby greatly improves the efficiency of the system by the attendant reduction of friction. More specifically, the tapered surface of the drum forces the rope coming on to the drum during a lifting operation to slide off the taper towards the front of the drum, so that there is always space created for new rope to come onto the rear of the drum. This action works more effectively with increased load and works very well with as little as ten pounds load. However, the tapered surface is less effective when simply retrieving rope with no load. Therefore, it is preferred to utilize a lower rope guide block along with the tapered rope drum to prevent overlapping under a no load raising situation.
In another aspect of the present invention, an improved arcuate rope guide cage is provided which solves the above described excessive space problems in that there is no longer sufficient space between the arcuate rope guide cage and the rope on the drum to allow the rope to overlap itself, and because the arcuate rope guide cage is longer and positioned much closer to the drum than the known arcuate guide rope cage so as not to allow the rope to slip between it and the drum.
The present invention also provides additional associated (optional) components which form part of an overall rescue system, with the above described hoist as the principal component thereof. The additional components described below have been designed to avoid additional problems which have been experienced with known rescue system components.
For example, another problem with existing rescue systems utilizing a hoist of the type described above is that if the operator should let go of the control end of the rope during a lower operation, the person being lowered will descend at a dangerously high speed. This invention therefore provides a centrifugal brake device for use with the hoist which constantly senses rope speed while lowering, and if an excessive speed is reached, the brake will automatically "grip" the rope and prevent further descent. The centrifugal brake device in accordance with an exemplary embodiment of this invention may be installed on the drum bracket or backplate via a mounting slot and appropriate fastening means. The system is assembled so that the rope coming off the drum passes through an opening in the centrifugal brake device. Within the device, there is a tapered rope wheel designed to engage the rope as the rope travels downwardly during a lowering operation. However, the natural tendency of the rope to travel along the drum during raising ensures that the rope will not contact the tapered rope wheel during a raising operation, and therefore, the device adds no additional friction during raising so that overall system efficiency is maintained.
In the exemplary embodiment, the rope coming off the rope drum during lowering will contact the tapered rope wheel causing the latter to spin with a horizontal shaft to which it is rigidly secured. A centrifugal disk is located at the other end of the shaft and mounts a pair of spring loaded pawls which are held in a normally retracted position by springs or the like. As lowering speed increases, the centrifugal disk rotational speed will increase to the point where the pawls will pivot radially outwardly overcoming the retraction force of the springs. Upon reaching a predetermined speed, the pawls will have moved radially outwardly sufficiently so that one of the pawls will contact the lower end of a vertical connecting rod and drive the latter into engagement with the lower surface of a rope locking cam. This rope locking cam is a wedge shaped component which is pivotally secured to the device so that, upon active engagement with the connecting rod, the rope cam will sandwich the rope between it and the roller drum, thereby stopping further movement of the rope. Once activated, the cam remains engaged and the person on the system remains stopped. In order to disengage the centrifugal brake and resume lowering, the operator must simply raise the load slightly thereby pulling the cam upwardly to release it, at which point, a spring associated with the cam will return the cam to its normal disengaged position. The centrifugal brake is thus automatically reset and ready for further activation if and when required.
Another problem with existing systems of the type described above is that when using the system for certain types of work or rescue, i.e., in a confined work space (entry into manholes, underground electrical vaults, tanks, etc.), the person connected to the system inevitably will twist the ropes by turning around naturally as he performs his work. A problem arises in that, if an emergency rescue (raising) must be performed, the twisting of the ropes causes large amounts of friction to occur and, depending on the degree of twist, may render the operator incapable of raising the person as the force required will be simply too great.
In still another aspect of the present invention, therefore, a swivel pulley is provided which allows the person connected to the hoist system to move and to rotate 360.degree. without twisting the ropes. The arrangement is such that the lower part of the swivel (connected via a conventional carabiner to the person) will turn, but the upper part connected to the pulley, ropes and hoist will not.
Another aspect of the rescue system in accordance with this invention relates to rope control handles or, as they are known in the art, "handled ascenders". Such devices are often used in mountain climbing to pull oneself up along an otherwise stationary rope. In rescue operations, handled ascenders may be used, for example, to haul on the rope, i.e., to lift a load from a control end of the rope. Existing handled ascenders are manufactured in right-hand and left-hand versions, with closed loop handles. The thumb or forefinger is is used to disengage a cam from the rope to allow the rope to slide through the ascender. A problem arises in that it is awkward to disengage the cam and, in fact, impossible to disengage the cam if wearing gloves or mitts, because the cam is located within a closed loop, accessible from either side of the ascender. In addition, having both left and right-handed versions makes it difficult for a person of the "opposite hand" to operate the ascender. The closed loop handle design of the existing ascenders also makes them difficult and often impossible to hold at all when wearing bulky gloves or mitts, as typically required in cold weather situations. In accordance with this invention, there is provided an improved handled ascender which features a cam design with an integral lever protruding from the rear of the ascender which can be operated with equal ease by a left or right-handed person, and which is very simple to operate even with large bulky gloves or mitts. An open handle design also allows even the largest mitted hands (either left or right) to easily hold and operate the ascender.
In broad terms, the invention thus provides a rescue system comprising a hoist including a backplate; a rope drum mounted on the backplate, the rope drum capable of rotation in one direction only; the rope drum having a front and rear end plates on either side of a rope engaging surface, the rope engaging surface including a cylindrical portion and a tapered portion, the tapered portion located adjacent the rear end plate; the hoist further comprising an arcuate rope guide including a thru slot fixed to the backplate and extending partially about the drum.
In another aspect, the invention provides a rescue system comprising: a hoist including a backplate; a rope drum mounted on the backplate, the rope drum having a rope engaging surface located between a pair of circular end flanges, the rope drum capable of rotation in a first direction in response to a pulling force applied to a control end of a rope wound around the rope drum at least one and one half times, and the drum being blocked against rotation in an opposite direction such that a frictional braking force is applied to the rope when a pulling force is applied to a load end of the rope in a second direction opposite the one direction; and a rope guide fixed to the backplate, the rope guide formed by a pair of elongated laterally spaced legs connected at opposite ends of the rope guide to define therebetween at least one rope slot, the rope guide having an arcuate shape conforming substantially to the circular end flanges of the rope drum, wherein the rope guide extends circumferentially at least 200.degree. about the end flange.
In still another aspect, the invention provides in a rescue system including a hoisting apparatus which includes a backplate, a rope drum mounted on the backplate, the rope drum adapted to receive a rope thereon, wound at least one and one half times about a rope engaging surface on the drum, the rope having a load end and a control end, the drum rotatable in one direction when a pulling force is exerted on the control end and blocked against rotation in an opposite direction when a pulling force is exerted on the load end such that the rope drum provides a braking force on the rope when the pulling force is exerted on the load end; an improvement comprising:
a) an arcuate rope guide fixed to the backplate and extending at least 200.degree. about the drum; and
b) the rope engaging surface including a cylindrical portion and a tapered portion, the tapered portion lying closest to the backplate.
It will be appreciated that the invention also relates to the utilization of the optional components including the centrifugal brake mechanism, the swivel pulley and the handled ascender as described generally above and as described in greater detail further herein.
Other objects and advantages of the invention over and above those described above will become apparent from the detailed description which follows.